Systems and methods for concurrent spectrum usage within actively used spectrum

ABSTRACT

Systems and methods are described to concurrently utilize actively used spectrum for new TDD or FDD networks, and also for enabling Distributed-Input Distributed Output (DIDO) techniques to be used with both the new networks and the existing networks in the same spectrum.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. ProvisionalPatent Application No. 61/980,479, filed, Apr. 16, 2014, entitled,“Systems And Methods For Concurrent Spectrum Usage Within Actively UsedSpectrum”.

This application may be related to the following co-pending U.S. PatentApplications and U.S. Provisional Applications:

U.S. Provisional Application Ser. No. 61/937,273, entitled “Systems andMethods for Mapping Virtual Radio Instances into Physical Areas toCoherence in Distributed Antenna Wireless Systems”

U.S. application Ser. No. 13/844,355, entitled “Systems and Methods forRadio Frequency Calibration Exploiting Channel Reciprocity inDistributed Input Distributed Output Wireless Communications”

U.S. application Ser. No. 13/797,984, entitled “Systems and Methods forExploiting Inter-cell Multiplexing Gain in Wireless Cellular Systems ViaDistributed Input Distributed Output Technology”

U.S. application Ser. No. 13/797,971, entitled “Systems and Methods forExploiting Inter-cell Multiplexing Gain in Wireless Cellular Systems ViaDistributed Input Distributed Output Technology”

U.S. application Ser. No. 13/797,950, entitled “Systems and Methods forExploiting Inter-cell Multiplexing Gain in Wireless Cellular Systems ViaDistributed Input Distributed Output Technology”

U.S. application Ser. No. 14/156,254, entitled “System and Method ForDistributed Antenna Wireless Communications”

U.S. application Ser. No. 14/086,700, entitled “Systems and Methods forExploiting Inter-cell Multiplexing Gain in Wireless Cellular Systems ViaDistributed Input Distributed Output Technology”

U.S. application Ser. No. 14/023,302, entitled “Systems And Methods ToCoordinate Transmissions In Distributed Wireless Systems Via UserClustering”

U.S. application Ser. No. 13/633,702, entitled “Systems and Methods forWireless Backhaul in Distributed-Input Distributed-Output WirelessSystems”

U.S. application Ser. No. 13/475,598, entitled “Systems and Methods toenhance spatial diversity in distributed-input distributed-outputwireless systems”

U.S. application Ser. No. 13/464,648, entitled “System and Methods toCompensate for Doppler Effects in Distributed-Input Distributed OutputSystems”

U.S. application Ser. No. 13/461,682, entitled “System and Method forAdjusting DIDO Interference Cancellation Based On Signal StrengthMeasurements”

U.S. application Ser. No. 13/233,006, entitled “System and Methods forplanned evolution and obsolescence of multiuser spectrum”

U.S. application Ser. No. 13/232,996, entitled “Systems and Methods toExploit Areas of Coherence in Wireless Systems”

U.S. application Ser. No. 12/802,989, entitled “System And Method ForManaging Handoff Of A Client Between DifferentDistributed-Input-Distributed-Output (DIDO) Networks Based On DetectedVelocity Of The Client”

U.S. application Ser. No. 12/802,988, entitled “Interference Management,Handoff, Power Control And Link Adaptation In Distributed-InputDistributed-Output (DIDO) Communication Systems”

U.S. application Ser. No. 12/802,975, entitled “System And Method ForLink adaptation In DIDO Multicarrier Systems”

U.S. application Ser. No. 12/802,974, entitled “System And Method ForManaging Inter-Cluster Handoff Of Clients Which Traverse Multiple DIDOClusters”

U.S. application Ser. No. 12/802,958, entitled “System And Method ForPower Control And Antenna Grouping In ADistributed-Input-Distributed-Output (DIDO) Network”

U.S. Pat. No. 8,654,815, to issue Feb. 18, 2014, entitled “System andMethod for Distributed Input Distributed Output Wireless Communications”

U.S. Pat. No. 8,571,086, issued Oct. 29, 2013, entitled “System andMethod for DIDO Precoding Interpolation in Multicarrier Systems”

U.S. Pat. No. 8,542,763, issued Sep. 24, 2013, entitled “Systems andMethods To Coordinate Transmissions In Distributed Wireless Systems ViaUser Clustering”

U.S. Pat. No. 8,428,162, issued Apr. 23, 2013, entitled “System andMethod for Distributed Input Distributed Output Wireless Communications”

U.S. Pat. No. 8,170,081, issued May 1, 2012, entitled “System And MethodFor Adjusting DIDO Interference Cancellation Based On Signal StrengthMeasurements”

U.S. Pat. No. 8,160,121, issued Apr. 17, 2012, entitled, “System andMethod For Distributed Input-Distributed Output WirelessCommunications”;

U.S. Pat. No. 7,885,354, issued Feb. 8, 2011, entitled “System andMethod For Enhancing Near Vertical Incidence Skywave (“NVIS”)Communication Using Space-Time Coding.”

U.S. Pat. No. 7,711,030, issued May 4, 2010, entitled “System and MethodFor Spatial-Multiplexed Tropospheric Scatter Communications”;

U.S. Pat. No. 7,636,381, issued Dec. 22, 2009, entitled “System andMethod for Distributed Input Distributed Output Wireless Communication”;

U.S. Pat. No. 7,633,994, issued Dec. 15, 2009, entitled “System andMethod for Distributed Input Distributed Output Wireless Communication”;

U.S. Pat. No. 7,599,420, issued Oct. 6, 2009, entitled “System andMethod for Distributed Input Distributed Output Wireless Communication”;

U.S. Pat. No. 7,418,053, issued Aug. 26, 2008, entitled “System andMethod for Distributed Input Distributed Output Wireless Communication”;

BACKGROUND

Both Frequency Division Duplex (“FDD”) and Time Division Duplex (“TDD”)modes are commonly used in wireless communications systems. For example,the LTE standard supports both FDD and TDD modes, as another example802.11 versions (e.g. Wi-Fi) support TDD mode of operation.

In the case of LTE, various numbered bands are defined within what iscalled “Evolved UMTS Terrestrial Radio Access” (E-UTRA) air interface.Each E-UTRA band not only specifies a particular band number, but itdefines whether the band is FDD or TDD, and what bandwidths aresupported within the band (e.g. seehttp://en.wikipedia.org/wiki/LTE_frequency_bands#Frequency_bands_and_channel_bandwidthsfor a list of E-UTRA bands and their specifications). For example, Band7 is an FDD band defined as using the frequency ranges of 2,500-2,570MHz for Uplink (“UL”), 2,620-2,690 for downlink (“DL”), it supports 5,10, 15, 20 and MHz signal bandwidths within each of the UL and DL bands.

In many cases E-UTRA bands overlap. For example, different bands may becommon spectrum that has been allocated in different markets or regions.For example, Band 41 is a TDD band using the frequency ranges of2,496-2,690 MHz for both UL and DL, which overlaps with both UL and DLranges in FDD Band 7. Currently, Band 41 is used in the U.S. by Sprint,while Band 7 is used by Rogers Wireless in the bordering country ofCanada. Thus, in the U.S., 2,500-2,570 MHz is TDD spectrum, while inCanada that same frequency range is UL for FDD spectrum.

Typically, a mobile device, upon attaching to a wireless network, willscan through the band searching for transmissions from one or more basestations, and typically during the attach procedure, the base stationwill transmit the characteristics of the network, such as the bandwidthused by the network, and details of the protocol in use. For example, ifan LTE device scans through 2,620-2,690 MHz in the U.S., it mightreceive an LTE DL frame transmitted by an eNodeB that identifies thespectrum as Band 41, and if the LTE device supports Band 41 and TDD, itmay attempt to connect to the eNodeB in TDD mode in that band.Similarly, if an LTE device scans through 2,620-2,690 MHz in the Canada,it might receive an LTE DL frame transmitted by an eNodeB thatidentifies the spectrum as Band 7, and if the LTE device supports Band 7and FDD, it may attempt to connect to the eNodeB in FDD mode in Band 7.

Most early LTE networks deployed worldwide used FDD mode (e.g., Verizon,AT&T), but increasingly TDD mode is being used, both in markets withextensive FDD coverage, such as the U.S. (where Sprint is deploying TDD)and in markets that do not yet have extensive LTE coverage, such asChina (where China Mobile is deploying TDD). In many cases, a singleoperator is deploying both FDD and TDD at different frequencies (e.g.Sprint operates both FDD LTE and TDD LTE in different frequencies in theU.S.), and may offer LTE devices which can operate in both modes,depending on which band is used.

Note that the E-UTRA list of LTE bands is by no means a final list, butrather evolves as new spectrum is allocated to mobile operators anddevices to use that spectrum are specified. New bands are specified bothin spectrum with no current band that overlaps its frequencies, and inspectrum in bands overlapping frequencies of previous band allocations.For example, Band 44, a TDD band spanning 703-803 MHz, was added as anE-UTRA band several years after older 700 MHz FDD bands were specified,such as Bands 12, 13, 14 and 17.

As can be seen in FIG. 6, the bulk of mobile data used to be voice data(e.g. Q1 2007), which is highly symmetric. But, with the introduction ofthe iPhone in 2007, and the rapid adoption of Android and thenintroduction of the iPad in 2009, non-voice mobile data rapidly outpacedthe growth of voice data, to the point where, by the middle of 2013,voice data was a small fraction of mobile data traffic. Non-voice datais projected to continue to grow exponentially, increasingly dwarfingvoice data.

As can been seen in FIG. 7, non-voice mobile data is largely dominatedby media, such as streaming video, audio and Web browsing (much of whichincludes streaming video). Although some streaming media is UL data(e.g. during a videoconference), the vast majority is DL data, resultingis highly asymmetric DL vs. UL data usage. For example, in the FinancialTimes May 28, 2013 article, “Asymmetry and the impending (US) spectrumcrisis”, it states that “ . . . industry estimates of the ratio of datatraffic downlink to data traffic in the uplink ranges from a ratio ofabout eight to one (8:1)—to considerably more.” The article then pointsout that the largely FDD deployments in the U.S. are very inefficient inhandling such asymmetry since FDD mode allocates the same amount ofspectrum to each DL and UL. As another example, Qualcomm estimated DL/ULtraffic asymmetry as high as 9:1 for one of the U.S. operators, based on2009 measurements in live networks (cfr., Qualcomm, “1000x: morespectrum—especially for small cells”, November 2013,http://www.qualcomm.com/media/documents/files/1000x-more-spectrum-especially-for-small-cells.pdf).Thus, even when FDD DL spectrum is heavily utilized (potentially to thepoint of being overloaded), the UL spectrum may be largely unused.

The Financial Times article points out that TDD is far better suited tosuch asymmetry since it can be configured to allocate far more timeslotsto the DL data than the UL data. For example, in the case when 20 MHz isallocated to FDD (as 10+10 MHz), DL data throughput is limited to amaximum of full-time use of 10 MHz (even when the UL data needs far lessthan the 10 MHz it has been allocated), whereas when 20 MHz allocated toTDD, DL data throughput can use all 20 MHz the vast majority of thetime, allocating the 20 MHz to UL data a small percentage of the time,far better matching the characteristics of data usage today. The articleacknowledges that, unfortunately, most existing U.S. mobile spectrum isalready committed to FDD mode, but urges the FCC to encourage the use ofTDD as it allocates new spectrum.

Although TDD would certainly allow for more efficient use of newspectrum allocations given the increasingly asymmetric nature of mobiledata, unfortunately existing FDD networks deployments cannot changeoperating mode to TDD since the vast majority of users of such LTE FDDnetworks have devices that only support FDD mode and their devices wouldcease to be able to connect if the network were switched to TDD mode.Consequently, as LTE data usage becomes increasingly asymmetric,existing LTE FDD networks will see increasing DL congestion, while ULspectrum will be increasingly underutilized (at 8:1 DL:UL ratio, thelower estimate of the May 28, 2013 Financial Times article, that wouldimply that if the DL channel is fully utilized, only ⅛^(th), equivalentto 1.25 MHz of 10 Mhz, would be used of the UL channel). This isextremely wasteful and inefficient, particularly given the limitedphysical existence of practical mobile spectrum (e.g. frequencies thatcan penetrate walls and propagate well non-line-of-sight, such as˜450-2600 MHz) and the exponential growth of (increasingly asymmetric)mobile data (e.g. Cisco February 2013 VNI predicts a 61% CAGR in mobiledata growth through 2018, most of which is streaming video and otherhighly asymmetric data).

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present invention can be obtained from thefollowing detailed description in conjunction with the drawings, inwhich:

FIG. 1 illustrates the general framework of the DIDO Radio AccessNetwork (DRAN)

FIG. 2 illustrates the protocol stack of the Virtual Radio Instance(VRI) consistent to the OSI model and LTE standard

FIG. 3 illustrates adjacent DRANs to extend coverage in DIDO wirelessnetworks

FIG. 4 illustrates handoff between DRAN and adjacent wireless networks

FIG. 5 illustrates handoff between DRAN and LTE cellular networks

FIG. 6 is prior art showing voice and non-voice data utilization ofmobile spectrum from 2007-2013.

FIG. 7 is prior art showing mobile data traffic share by applicationtype in 2012.

FIG. 8 is a prior art comparison of FDD LTE and TDD LTE modes ofoperations

FIG. 9 illustrates a new TDD network concurrently using UL spectrum withan existing FDD network

FIG. 10 is a prior art chart of TDD LTE duplex configurations

FIG. 11 illustrates a new TDD network concurrently using DL spectrumwith an existing FDD network

FIG. 12 illustrates a two new TDD networks concurrently using UL and DLspectrum with an existing FDD network

FIG. 13 illustrates a new FDD network concurrently using UL and DLspectrum with an existing FDD network

DETAILED DESCRIPTION

One solution to overcome many of the above prior art limitations is tohave user devices concurrently operate in TDD mode in the same spectrumas currently used UL or DL FDD spectrum, such that the TDD spectrumusage is coordinated so as to not conflict with current FDD spectrumusage. Particularly in the FDD UL channel, there is increasingly moreunused spectrum, and TDD devices could use that spectrum withoutimpacting the throughput of the existing FDD network. The also enablesTDD usage highly propagation-efficient UHF spectrum which, in manyregions of the world is almost entirely allocated to FDD, relegating TDDto far less propagation-efficient microwave bands.

In another embodiment is to have user devices concurrently operated inFDD mode in the same spectrum as currently used UL or DL FDD spectrum,such that the UL and DL channels are reversed and each network'sspectrum usage is coordinated so as not to conflict with the othernetwork's spectrum usage. Given that the UL channel of each network isincreasingly underutilized relative to the DL channel, it allows eachnetwork's DL channel to utilize the unused spectrum in the othernetwork's UL channel.

Further, in either embodiment spectral efficiency can be vastlyincreased by implementing one or both networks using Distributed-InputDistributed-Output (“DIDO”) technology as described in the followingpatents, patent applications and provisional applications, all of whichare assigned the assignee of the present patent and are incorporated byreference. These patents, applications and provisional applications aresometimes referred to collectively herein as the “Related Patents andApplications.”

U.S. Provisional Application Ser. No. 61/937,273, entitled “Systems andMethods for Mapping Virtual Radio Instances into Physical Areas toCoherence in Distributed Antenna Wireless Systems”

U.S. application Ser. No. 14/156,254, entitled “System and Method ForDistributed Antenna Wireless Communications”

U.S. application Ser. No. 14/086,700, entitled “Systems and Methods forExploiting Inter-cell Multiplexing Gain in Wireless Cellular Systems ViaDistributed Input Distributed Output Technology”

U.S. application Ser. No. 14/023,302, entitled “Systems And Methods ToCoordinate Transmissions In Distributed Wireless Systems Via UserClustering”

U.S. application Ser. No. 13/844,355, entitled “Systems and Methods forRadio Frequency Calibration Exploiting Channel Reciprocity inDistributed Input Distributed Output Wireless Communications”

U.S. application Ser. No. 13/797,984, entitled “Systems and Methods forExploiting Inter-cell Multiplexing Gain in Wireless Cellular Systems ViaDistributed Input Distributed Output Technology”

U.S. application Ser. No. 13/797,971, entitled “Systems and Methods forExploiting Inter-cell Multiplexing Gain in Wireless Cellular Systems ViaDistributed Input Distributed Output Technology”

U.S. application Ser. No. 13/797,950, entitled “Systems and Methods forExploiting Inter-cell Multiplexing Gain in Wireless Cellular Systems ViaDistributed Input Distributed Output Technology”

U.S. application Ser. No. 13/633,702, entitled “Systems and Methods forwireless backhaul in distributed-input distributed-output wirelesssystems”

U.S. application Ser. No. 13/475,598, entitled “Systems and Methods toenhance spatial diversity in distributed-input distributed-outputwireless systems”

U.S. application Ser. No. 13/464,648, entitled “System and Methods toCompensate for Doppler Effects in Distributed-Input Distributed OutputSystems”

U.S. application Ser. No. 13/233,006, entitled “System and Methods forplanned evolution and obsolescence of multiuser spectrum”

U.S. application Ser. No. 13/232,996, entitled “Systems and Methods toExploit Areas of Coherence in Wireless Systems”

U.S. application Ser. No. 12/802,989, entitled “System And Method ForManaging Handoff Of A Client Between DifferentDistributed-Input-Distributed-Output (DIDO) Networks Based On DetectedVelocity Of The Client”

U.S. application Ser. No. 12/802,988, entitled “Interference Management,Handoff, Power Control And Link Adaptation In Distributed-InputDistributed-Output (DIDO) Communication Systems”

U.S. application Ser. No. 12/802,975, entitled “System And Method ForLink adaptation In DIDO Multicarrier Systems”

U.S. application Ser. No. 12/802,974, entitled “System And Method ForManaging Inter-Cluster Handoff Of Clients Which Traverse Multiple DIDOClusters”

U.S. application Ser. No. 12/802,958, entitled “System And Method ForPower Control And Antenna Grouping In ADistributed-Input-Distributed-Output (DIDO) Network”

U.S. Pat. No. 8,654,815, issued Feb. 18, 2014, entitled “System andMethod for Distributed Input Distributed Output Wireless Communications”

U.S. Pat. No. 8,571,086, issued Oct. 29, 2013, entitled “System andMethod for DIDO precoding interpolation in multicarrier systems”

U.S. Pat. No. 8,542,763, issued Sep. 24, 2013, entitled “Systems andMethods to coordinate transmissions in distributed wireless systems viauser clustering”

U.S. Pat. No. 8,428,162, issued Apr. 23, 2013, entitled “System andMethod for Distributed Input Distributed Output Wireless Communication”

U.S. Pat. No. 8,170,081, issued May 1, 2012, entitled “System And MethodFor Adjusting DIDO Interference Cancellation Based On Signal StrengthMeasurements”

U.S. Pat. No. 8,160,121, issued Apr. 17, 2012, entitled, “System andMethod For Distributed Input-Distributed Output WirelessCommunications”;

U.S. Pat. No. 7,885,354, issued Feb. 8, 2011, entitled “System andMethod For Enhancing Near Vertical Incidence Skywave (“NVIS”)Communication Using Space-Time Coding.”

U.S. Pat. No. 7,711,030, issued May 4, 2010, entitled “System and MethodFor Spatial-Multiplexed Tropospheric Scatter Communications”;

U.S. Pat. No. 7,636,381, issued Dec. 22, 2009, entitled “System andMethod for Distributed Input Distributed Output Wireless Communication”;

U.S. Pat. No. 7,633,994, issued Dec. 15, 2009, entitled “System andMethod for Distributed Input Distributed Output Wireless Communication”;

U.S. Pat. No. 7,599,420, issued Oct. 6, 2009, entitled “System andMethod for Distributed Input Distributed Output Wireless Communication”;

U.S. Pat. No. 7,418,053, issued Aug. 26, 2008, entitled “System andMethod for Distributed Input Distributed Output Wireless Communication”;

The present invention discloses systems and methods for concurrentspectrum usage within actively used spectrum. Some of the embodimentsutilize Distributed-Input Distributed-Output and MU-MAS technologypreviously disclosed by the assignee of the assignee of the presentpatent. The disclosures in Section 1 and Section 2 below correspond tothe disclosures in the U.S. Provisional Application Serial No. #####filed, entitled “Systems and Methods for Mapping Virtual Radio Instancesinto Physical Areas to Coherence in Distributed Antenna WirelessSystems” and relate to the present invention.

1. Systems and Methods for Mapping VRIs into Areas of Coherence

One embodiment of the present invention discloses systems and methods todeliver multiple simultaneous non-interfering data streams within thesame frequency band between a network and a plurality of areas ofcoherence in a wireless link through Virtual Radio Instances (VRIs). Inone embodiment the system is a multiuser multiple antenna system(MU-MAS) as depicted in FIG. 1. The color-coded units in FIG. 1 showone-to-one mapping between the data sources 101, the VRIs 106 and theareas of coherence 103 as described hereafter.

1.1 Overview of the System Architecture

In FIG. 1, the data sources 101 are data files or streams carrying webcontent or files in a local or remote server, such as text, images,sounds, videos or combinations of those. One or multiple data files orstreams are sent or received between the network 102 and every area ofcoherence 103 in the wireless link 110. In one embodiment the network isthe Internet or any wireline or wireless local area network.

The area of coherence is a volume in space where the waveforms fromdifferent antennas of the MU-MAS add up coherently in a way that onlythe data output 112 of one VRI is received within that area ofcoherence, without any interference from other data output from otherVRIs sent simultaneously over the same wireless link. In the presentapplication we use the term “area of coherence” to describe volumes ofcoherence or private cells (e.g., “pCells™” 103) as described in ourprevious patent application [U.S. application Ser. No. 13/232,996,entitled “Systems and Methods to Exploit Areas of Coherence in WirelessSystems”]. In one embodiment, the areas of coherence correspond to thelocations of the user equipment (UE) 111 or subscribers of the wirelessnetwork, such that every subscriber is associated to one or multipledata sources 101. The areas of coherence may vary in size and shapedepending on propagation conditions as well as type of MU-MAS precodingtechniques employed to generate them. In one embodiment of theinvention, the MU-MAS precoder dynamically adjusts size and shape of theareas of coherence to adapt to the changing propagation conditions whiledelivering contents to the users with good link reliability.

The data sources 101 are first sent through the Network 102 to the DIDORadio Access Network (DRAN) 104. Then, the DRAN translates the datafiles or streams into a data format that can be received by the UEs andsends the data files or streams simultaneously to the plurality of areasof coherence, such that every UE receives its own data files or streamswithout interference from other data files or streams sent to other UEs.The DRAN consists of a gateway 105 as the interface between the networkand the VRIs 106. The VRIs translate packets being routed by the gatewayinto data streams 112, either as raw data, or in a packet or framestructure, that are fed to a MU-MAS baseband unit. In one embodiment,the VRI comprises the open systems interconnection (OSI) protocol stackconsisting of sever layers: application, presentation, session,transport, network, data link and physical, as depicted in FIG. 2a . Inanother embodiment, the VRI only comprises a subset of the OSI layers.

In another embodiment, the VRIs are defined from different wirelessstandards. By way of example, but not limitation, a first VRI consistsof the protocol stack from the GSM standard, a second VRI from the 3Gstandard, a third VRI from HSPA+ standard, a fourth VRI from LTEstandard, as fifth VRI from LTE-A standard and a sixth VRI from theWi-Fi standard. In an exemplary embodiment, the VRIs comprise thecontrol-plane or user-plane protocol stack defined by the LTE standards.The user-plane protocol stack is shown in FIG. 2b . Every UE 202communicates with its own VRI 204 through the PHY, MAC, RLC and PDCPlayers, with the gateway 203 through the IP layer and with the network205 through the application layer. For the control-plane protocol stack,the UE also communicates directly with the mobility management entity(MME) through the NAS (as defined in the LTE standard stack) layer.

The Virtual Connection Manager (VCM) 107 is responsible for assigningthe PHY layer identity of the UEs (e.g., cell-specific radio networktemporary identifier, RNTI), authentication and mobility of the VRI andUE. The data streams 112 at the output of the VRIs are fed to theVirtual Radio Manager (VRM) 108. The VRM comprises a scheduler unit(that schedules DL (downlink) and UL (uplink) packets for differentUEs), a baseband unit (e.g., comprising of FEC encoder/decoder,modulator/demodulator, resource grid builder) and a MU-MAS basebandprocessor (comprised of precoding logic for implementing precodingoperations). In one embodiment, the data streams 112 are I/Q samples atthe output of the PHY layer in FIG. 2b that are processed by the MU-MASbaseband processor. In a different embodiment, the data streams 112 areMAC, RLC or PDCP packets sent to a scheduler unit that forwards them toa baseband unit. The baseband unit converts packets into I/O fed to theMU-MAS baseband processor.

The MU-MAS baseband processor is the core of the VRM that converts the MI/Q samples from the M VRIs into N data streams 113 sent to N accesspoints (APs) 109. In one embodiment, the data streams 113 are I/Qsamples of the N waveforms transmitted over the wireless link 110 fromthe APs 109. In this embodiment the AP consists of ADC/DAC, RF chain andantenna. In a different embodiment, the data streams 113 are bits ofinformation and MU-MAS precoding information that are combined at theAPs to generate the N waveforms sent over the wireless link 110. In thisembodiment every AP is equipped with CPU, DSP or SoC to carry outadditional baseband processing before the ADC/DAC units.

1.2 Supporting Mobility and Handoff

The systems and methods described thus far work as long the UEs arewithin reach of the APs. When the UEs travel away from the AP coveragearea the link may drop and the DRAN 301 is unable to create areas ofcoherence. To extend the coverage area, the systems can gradually evolveby adding new APs. There may not be enough processing power in the VRM,however, to support the new APs or there may be practical installationissues to connect the new APs to the same VRM. In these scenarios, it isnecessary to add adjacent DRANs 302 and 303 to support the new APs asdepicted in FIG. 3.

In one embodiment a given UE is located in the coverage area served bythe first DRAN 301 and the adjacent DRAN 302. In this embodiment, theadjacent DRAN 302 only carries out MU-MAS baseband processing for thatUE, jointly with the MU-MAS processing from the first DRAN 301. No VRIis handled by the adjacent DRAN 302 for the given UE, since the VRI forthat UE is already running within the first DRAN 301. To enable jointprecoding between the first and adjacent DRANs, baseband information isexchanged between the VRM in the first DRAN 301 and the VRM in theadjacent DRAN 302 through the cloud-VRM 304 and the links 305. The links305 are any wireline (e.g., fiber, DSL, cable) or wireless link (e.g.,line-of-sight links) that can support adequate connection quality (e.g.low enough latency and adequate data rate) to avoid degradingperformance of the MU-MAS precoding.

In a different embodiment a given UE moves out of the coverage area ofthe first DRAN 301 into the coverage area of the adjacent DRAN 303. Inthis embodiment the VRI associated to that UE is “teleported” from thefirst DRAN 301 to the adjacent DRAN 303. What is meant by the VRI beingteleported or “VRI teleportation” is the VRI state information istransferred from DRAN 301 to DRAN 303, and the VRI ceases to executewithin DRAN 301 and begins to execute within DRAN 303. Ideally, the VRIteleportation occurs fast enough that, from the perspective of the UEserved by the teleported VRI, it does not experience any discontinuityin its data stream from the VRI. In one embodiment, if there is a delaybefore the VRI is fully executing after being teleported, then beforethe VRI teleportation begins, the UE served by that VRI is put into astate where it will not drop its connection or otherwise enter anundesirable state until the VRI starts up at the adjacent DRAM 303, andthe UE once again is served by an executing VRI. “VRI teleportation” isenabled by the cloud-VCM 306 that connects the VCM in the first DRAN 301to the VCM in the adjacent DRAN 303. The wireline or wireless links 307between VCM do not have the same restrictive constraints as the links305 between VRMs since they only carry data and do not affectperformance of the MU-MAS precoding. In the same embodiment of theinvention, additional links 305 are employed between the first DRAN 301and the adjacent DRAN 303 to connect their VRMs that can supportadequate connection quality (e.g., low enough latency and adequate datarate) to avoid degrading performance of the MU-MAS precoding. In oneembodiment of the invention, the gateways of the first and adjacentDRANs are connected to the cloud-gateway 308 that manages all networkaddress (or IP address) translation across DRANs.

In one embodiment of the invention, VRI teleportation occurs between theDRAN network disclosed in the present application and any adjacentwireless network 401 as depicted in FIG. 4. By way of example, but notlimitation, the wireless network 401 is any conventional cellular (e.g.,GSM, 3G, HSPA+, LTE, LTE-A) or wireless local area network (WLAN, e.g.,Wi-Fi). As the VRI is teleported from the DRAN to the adjacent wirelessnetwork 401 the UE is handed off between the two networks and itswireless connection may continue.

In one embodiment, the adjacent wireless network 401 is the LTE networkshown in FIG. 5. In this embodiment, the Cloud-VCM 502 is connected tothe LTE mobility management entity (MME) 501. All the information aboutidentity, authentication and mobility of every UE handing-off betweenthe LTE and the DRAN networks is exchanged between the MME 501 and thecloud-VCM 502. In the same embodiment, the MME is connected to one ormultiple eNodeBs 503 connecting to the UE 504 through the wirelesscellular network. The eNodeBs are connected to the network 507 throughthe serving gateway (S-GW) 505 and the packet data network gateway(P-GW) 506.

2. Systems and Methods for DL and UL MU-MAS Processing

Typical downlink (DL) wireless links consist of broadcast physicalchannels carrying information for the entire cell and dedicated physicalchannels with information and data for given UE. For example, the LTEstandard defines broadcast channels such as P-SS and S-SS (used forsynchronization at the UE), MIB and PDCCH as well as channels forcarrying data to given UE such as the PDSCH. In one embodiment of thepresent invention, all the LTE broadcast channels (e.g., P-SS, S-SS,MIC, PDCCH) are precoded such that every UE receives its own dedicatedinformation. In a different embodiment, part of the broadcast channel isprecoded and part is not. By way of example, but not limitation, thePDCCH contains broadcast information as well as information dedicated toone UE, such as the DCI 1A and DCI 0 used to point the UEs to theresource blocks (RBs) to be used over DL and uplink (UL) channels. Inone embodiment, the broadcast part of the PDCCH is not precoded, whereasthe portion containing the DCI 1A and 0 is precoded in such a way thatevery UE obtains its own dedicated information about the RBs that carrydata.

In another embodiment of the invention, precoding is applied to all oronly part of the data channels, such as the PDSCH in LTE systems. Byapplying precoding over the entire data channel, one embodiment of theMU-MAS disclosed in the present application allocates the entirebandwidth to every UE and the plurality of data streams of the pluralityof UEs are separated via spatial processing. In typical scenarios,however, most, if not all, of the UEs do not need the entire bandwidth(e.g., ˜70 Mbps per UE, peak data rate for TDD configuration #2 in 20MHz of spectrum). Then, one embodiment of the MU-MAS in the presentapplication subdivides the DL RBs in multiple blocks as in OFDMA systemsand assigns each block to a subset of UEs. All the UEs within the sameblock are separated through the MU-MAS precoding. In another embodiment,the MU-MAS allocates different DL subframes to different subsets of UEs,thereby dividing up the DL as in TDMA systems. In yet anotherembodiment, the MU-MAS both subdivides the DL RBs in multiple blocks asin OFDMA systems among subsets of UEs and also allocates different DLsubframes to different subsets of UEs as in TDMA systems, thus utilizingboth OFDMA and TDMA to divide up the throughput. For example, if thereare 10 APs in a TDD configuration #2 in 20 MHz, then there is anaggregate DL capacity of 70 Mbps*10=700 Mbps. If there are 10 UEs, theneach UE could receive 70 Mbps concurrently. If there are 200 UEs, andthe aggregate throughput is to be divided up equally, then using OFDMA,TDMA or a combination thereof, the 200 UEs would be divided into 20groups of 10 UEs, whereby each UE would receive 700 Mbps/200=3.5 Mbps.As another example, if 10 UEs required 20 Mbps, and the other UEs wereto evenly share the remaining throughput, then 20 Mbps*10=200 Mbps ofthe 700 Mbps would be used for 10 UEs, leaving 700 Mbps-200 Mbps=500Mbps to divide among the remaining 200−10=190 UEs. As such, each of theremaining 90 UEs would receive 500 Mbps/190=2.63 Mbps. Thus, far moreUEs than APs can be supported in the MU-MAS system of the presentinvention, and the aggregate throughput of all the APs can be dividedamong the many UEs.

In the UL channel, the LTE standard defines conventional multiple accesstechniques such as TDMA or SC-FDMA. In one embodiment of the presentinvention, the MU-MAS precoding is enabled over the DL in a way toassign UL grants to different UEs to enable TDMA and SC-FDMA multipleaccess techniques. As such, the aggregate UL throughput can be dividedamong far more UEs than there are APs.

When there are more UEs than there are APs and the aggregate throughputis divided among the UEs, as described above, in one embodiment, theMU-MAS system supports a VRI for each UE, and the VRM controls the VRIssuch that VRIs utilize RBs and resource grants in keeping with thechosen OFDMA, TDMA or SC-FDMA system(s) used to subdivide the aggregatethroughput. In another embodiment, one or more individual VRIs maysupport multiple UEs and manage the scheduling of throughput among theseUEs via OFDMA, TDMA or SC-FDMA techniques.

In another embodiment, the scheduling of throughput is based on loadbalancing of user demand, using any of many prior art techniques,depending upon the policies and performance goals of the system. Inanother embodiment, scheduling is based upon Quality of Service (QoS)requirements for particular UEs (e.g. that pay for a particular tier ofservice, guaranteeing certain throughput levels) or for particular typesof data (e.g. video for a television service).

In a different embodiment, UL receive antenna selection is applied toimprove link quality. In this method, the UL channel quality isestimated at the VRM based on signaling information sent by the UEs(e.g., SRS, DMRS) and the VRM decides the best receive antennas fordifferent UEs over the UL. Then the VRM assigns one receive antenna toevery UE to improve its link quality. In a different embodiment, receiveantenna selection is employed to reduce cross-interference betweenfrequency bands due to the SC-FDMA scheme. One significant advantage ofthis method is that the UE would transmit over the UL only to the APclosest to its location. In this scenario, the UE can significantlyreduce its transmit power to reach the closest AP, thereby improvingbattery life. In the same embodiment, different power scaling factorsare utilized for the UL data channel and for the UL signaling channel.In one exemplary embodiment, the power of the UL signaling channel(e.g., SRS) is increased compared to the data channel to allow UL CSIestimation and MU-MAS precoding (exploiting UL/DL channel reciprocity inTDD systems) from many APs, while still limiting the power required forUL data transmission. In the same embodiment, the power levels of the ULsignaling and UL data channels are adjusted by the VRM through DLsignaling based on transmit power control methods that equalize therelative power to/from different UEs.

In a different embodiment, maximum ratio combining (MRC) is applied atthe UL receiver to improve signal quality from every UE to the pluralityof APs. In a different embodiment zero-forcing (ZF) or minimum meansquared error (MMSE) or successive interference cancellation (SIC) orother non-linear techniques or the same precoding technique as for theDL precoding are applied to the UL to differentiate data streams beingreceived from different UEs' areas of coherence. In the same embodiment,receive spatial processing is applied to the UL data channel (e.g.,PUSCH) or UL control channel (e.g., PUCCH) or both.

3. Systems and Methods for Concurrent Spectrum Usage within ActivelyUsed Spectrum

As detailed in the Background section above, and shown in FIG. 6 andFIG. 7 mobile data usage has changed dramatically from being dominatedby largely symmetric voice data to highly asymmetric non-voice data,particularly media such as video streaming. Most mobile LTE deploymentsworldwide are FDD LTE, whose physical layer structure is illustrated inthe upper half of FIG. 8, which have fixed, symmetric uplink (“UL”) anddownlink (“DL”) channels, and as a result, as the DL channels havebecome increasingly congested with exponential growth of DL datarelative to UL data, the UL data channels have been increasinglyunderutilized.

The LTE standard also supports TDD LTE (also called “TD-LTE”) whosephysical layer structure is illustrated in the lower half of FIG. 8, andthe mobile operator can choose whether the UL and DL channels aresymmetric (as shown in this illustration) or asymmetric (e.g. with moresubframes allocated to either the DL or UL channel), and as a result, asthe DL channels become increasingly congested with exponential growth ofDL data relative to UL data, the mobile operator can choose to allocatemore subframes to DL than to UL. For example, in one configurationTD-LTE supports an 8:1 DL:UL ratio, allocating 8 times as many subframesto DL as to UL.

Other than the fact that TD-LTE is bi-directional in one channel, thestructure and details of TD-LTE and FDD LTE are almost identical. Inboth modes every frame has 10 ms duration and consists of ten subframesof 1 ms each. The modulation and coding schemes are almost identical,and the upper layers of the protocol stack are effectively the same. Inboth cases, the time and frequency reference for the user equipment(“UE”) devices (e.g. mobile phones, tablets) is provided by the eNodeB(the LTE base station protocol stack) to all devices (via the DL channelwith FDD LTE and during DL subframes with TD-LTE).

Notably, in the case of both FDD and TDD LTE, the network can beconfigured so that a UE may only transmit UL data when given a grant todo so by the eNodeB, received through a DL transmission. As such, theeNodeB not only controls when it transmits DL data, but it also controlswhen UEs may transmit UL data.

Also, notably, in the case of an LTE FDD UE, its receiver is only tunedto its DL channel and has no receiver tuned to its UL channel. As suchan FDD UE is “deaf” to anything that is transmitted in its UL channel byanother device.

And, in the case of all LTE UEs, whether FDD or TDD, even to the extenttheir receivers are tuned to a particular channel, other than certaincontrol signals intended for all UEs (or for a given UE) which maintaintheir time reference and connection to the network, or give themdirections at what time and frequency they are to receive data, theyignore DL data not intended to them. Or to put it another way, the onlyrelevant DL data to an LTE UE is data that is either control informationor is data that is directed to the UE. During other times, whether thechannel is utilized with a DL to another UE, not utilized at all orutilized for a purpose that falls outside of the LTE standard, the UE is“deaf” to any DL transmissions that are not control information or DLdata directed to that UE. Thus, LTE receivers, whether FDD or TDD, onlyreceive control data intended for all UEs or for a given UE, or receivedata for a given UE. Other transmissions in the DL channel are ignored.

FIG. 9 illustrates how an FDD and TDD network can concurrently utilizeactively utilize FDD spectrum. The top two lines of boxes labeled “FDDLTE 910” illustrate one LTE frame interval (10 ms) made up of ten 1 mssubframe intervals, in both the Uplink (“UL”) and Downlink (“DL”)channels. This illustration shows the type of asymmetric datatransmission that is increasingly more typical (e.g. downlink streamingvideo) where there is far more DL data than UL data. Boxes with solidoutlines filled with slanted lines (e.g. box 912 and boxes 911) indicatesubframes where data is being transmitted, boxes with dotted outlinesthat are blank (e.g. boxes 914) show “idle” subframes were no data isbeing transmitted (i.e. there are no transmissions in the channel duringthat subframe interval). Boxes 911 are 2 of the 10 DL subframes, all ofwhich are full of data. Box 912 shows 1 UL subframe which has data. Andboxes 914 are 3 of the 9 idle UL subframes which have no datatransmissions.

The middle two lines of boxes in FIG. 9 labeled “TDD LTE 920” illustrateone LTE frame interval (10 ms) made up of 10 1 ms subframe intervals,including 2 “Special” subframe intervals, but unlike the FDD LTE 910lines, both lines of boxes in the TDD LTE 920 line not only share thesame spectrum with each other, but they share the same spectrum as theFDD Uplink. This illustration shows asymmetric data transmission wherethere are 4 DL subframes and 3 UL subframes transmitting data. Boxeswith solid outlines filled with dashed lines (e.g. box 921, box 922 andbox 923) indicate subframes where data is being transmitted, the boxwith a dotted outline that is blank (i.e. box 924) shows an idlesubframe were no data is being transmitted (i.e. there are notransmissions in the channel during that subframe interval). Box 921 is1 of 4 DL subframes, all of which are full of data. Box 922 shows 1 of 3UL subframes all of which have data. Box 924 is the 1 idle UL subframewhich is empty.

The third two lines of boxes in FIG. 9 labeled “FDD+TDD LTE 930”illustrate one LTE frame interval (10 ms) made up of 10 1 ms subframeintervals, including 2 “Special” subframe intervals, and shows theconcurrent operation of the FDD LTE 910 system and the TDD LTE 920system, with the TDD LTE 920 system sharing the same spectrum as the FDDLTE 910 Uplink. The two systems do not interfere with each otherbecause, (a) during the subframe interval 912 where the FDD LTE 910system has UL data transmission, the TDD LTE 920 system has an idleinterval 924 when it is neither an UL or DL and (b) during the subframeintervals where the TDD LTE 920 system has transmissions in either theUL or DL direction (e.g. 921, 923 and 922), the FDD LTE 910 system hasidle UL intervals (e.g. idle UL subframes 914) with no UL datatransmissions. Thus, the two systems coexist using the same spectrumwith no interference between them.

For FDD LTE 910 and TDD LTE 920 networks to concurrently use the samespectrum, their operation must be coordinated by either one eNodeB thatis set up to operate two spectrum sharing networks concurrently, or bythe coordination of an eNodeB operating the existing TDD LTE 920 networkand a second network controller that could be a second eNodeB or anothersystem compatible with LTE timing and frame structure, such as theDistributed-Input Distributed-Output Distributed antenna MU-MAS C-RANsystem disclosed in Sections 1 and 2 above and in the Related Patentsand Applications. In any of these cases, both the frames of the FDD LTE910 and TDD LTE 920 systems have to be synchronized, not only in termsof timing, but in terms of subframe resource allocations. For example,in the case of FIG. 9, the system controlling the FDD LTE 910 systemwill need to be aware of which subframes are TDD UL subframes that areavailable to be used for UL (e.g. will not conflict with TDD DL controlsignals sent over subframes #0 and #5 for time and frequencysynchronization at the UE), and use one of those subframes for its FDDUL subframe 912. If the same system is also controlling the TDD LTE 920system, it will also have to be sure not to schedule an UL from a TDDdevice during that subframe 912, and if it is not controlling the TDDLTE 920 system, it will have to notify whatever system is controllingthe TDD LTE 920 system to not schedule an UL from a TDD device duringthat subframe 912. Of course, it may be the case that the FDD LTE 910system requires more than one UL subframe during a frame time, and ifso, its controller would use any or all of the 3 TDD LTE 920 subframes922 for its UL subframes, appropriately controlling or notifying asdescribed above. Note that it may be the case that in some 10 ms framesall of the UL subframes are allocated to one of the networks and theother network gets no UL subframes. LTE devices do not expect to be ableto transmit UL data every frame time (e.g. when an LTE network iscongested, an LTE device may wait many frame times before it is grantedeven a portion of a UL subframe), so one embodiment of the presentinvention will function when all of the available TDD LTE 920 ULsubframes in a given frame are utilized by one network (i.e. “starving”the other network of UL subframes). However, starving one network fortoo many successive frames or allowing too few UL frames in aggregatewill result in poor network performance (e.g., low UL throughput, orhigh round-trip latency) and, at some point, if the LTE devices attachedto the network seeking to transmit UL data may determine the network isnot usable and disconnect. As such, establishing appropriate schedulingpriorities and paradigms to balance the UL subframe resources betweenthe FDD LTE 910 and TDD LTE 920 networks may result in the best overallnetwork performance and user (and/or UE) experience.

One tool that is available for balancing the UL subframe resources (andto meet network operator priorities) that is not available in astandalone FDD LTE system are the TDD LTE Duplex Configurations shown inFIG. 10. FIG. 9 illustrates TDD LTE 920 system TDD LTE DuplexConfiguration 1, in which during the 10 subframes in the 10 ms frame,there are 4 UL subframes, 4 DL subframes and 2 Special subframes. As canbe seen in FIG. 10, there are several TDD LTE Duplex Configurationswhich can be used, depending on the mobile operator's needs and datatraffic patterns, and for balancing the UL subframe resources with theFDD LTE 910 network needs. The TDD LTE Duplex Configuration can also bechanged over time as data traffic patterns change. Any of the TDD LTEDuplex Configurations can be used with the present invention. Forexample, in Configuration 1, as shown in FIG. 9, 1 UL subframe has beenallocated to the FDD network and 3 UL subframes have been assigned tothe TDD network. If the FDD network had a sudden need for more ULthroughput, then 2 UL subframes can be allocated for FDD, leaving 2 forTDD, the very next frame time. So, switching UL subframe allocationbetween the FDD and TDD network can be extremely dynamic.

Note that, if desired, UL resource allocation between the FDD LTE 910and TDD LTE 920 networks can be even more fine-grained than a subframebasis. It is possible to allocate some resource blocks within a singlesubframe to FDD devices and others to TDD devices. For example, the LTEstandard employs SC-FDMA multiple access technique for the UL channel.As such, UL channels from FDD and TDD devices can be assigned todifferent resource blocks within the same subframe via SC-FDMA scheme.

Finally, it is possible to schedule an FDD LTE 910 UL during what wouldbe a TDD LTE 920 DL or Special subframe. One consideration is that TDDDL control signals used by the TDD LTE UEs to maintain their connectionsand maintain timing (e.g., P-SS and S-SS broadcast signaling sent oversubframes #0 and #5) must be received by the TDD LTE UEs with sufficientregularity or else the UEs may disconnect.

FIG. 11 shows the same concept in FIG. 9 and described above, except theshared channel is the FDD DL channel, not the FDD UL channel. The samesubframe filling and outlining designations from FIG. 9 are used in FIG.11 and as can be seen, the FDD traffic situation is reversed with all ofthe subframes of FDD LTE 1110 UL channel being used for data while only1 of the FDD LTE 1110 DL subframes is used for data, while all of theother DL subframes are “idle” and not transmitting data. Similarly, allof the TDD LTE 1120 UL subframes are used for data, while all but one ofthe TDD LTE 1120 DL subframes are used for data, and in this case theTDD LTE 1120 LTE channel is the same frequency as the FDD LTE 1110 DLchannel. The result of the combined FDD LTE 1110 and TDD LTE 1120networks is shown in the FDD+TDD LTE 1120 channels. As with the examplein FIG. 9 the two networks can be controlled by a single controller orby coordination of multiple controllers, with scheduling between them tobe sure both networks operate as desired by the network operator withadequate performance to the users and user devices.

Note that the FDD devices attached to the FDD LTE 1110 network arerelying on DL transmissions for control and timing information, as wellas for data and they must receive adequate control signals on asufficiently regular basis to remain connected. In one embodiment of theinvention, the FDD devices use the broadcast signaling sent by the TDDLTE 1120 network over the DL subframes (e.g., subframes #0 and #5) toobtain time and frequency synchronization. In a different embodiment,subframes #0 and #5 carrying broadcast signaling are assigned to the FDDLTE 1110 network and used to derive time and frequency synchronizationat every FDD device.

Although, as described above, typically the FDD DL channel is far morecongested than the FDD UL channel, there may be reasons why a mobileoperator wishes to share the DL channel. For example, some UL channelsare limited to only UL use by the spectrum regulating authority (e.g.there may be concerns about output power interfering with adjacentbands). Also, once a mobile operator begins to offer TDD devicescompatible with its FDD spectrum, the mobile operator will likely findthese devices to be using spectrum more efficiently than FDD devicesand, as such, may discontinue sales of FDD devices. As old FDD devicesgradually are replaced and an increasing percentage of devices are TDD,the operator may wish to allocate increasingly more of its spectrum toTDD devices, but still maintain compatibility with the remaining FDDdevices in the market.

Toward this end, as there are fewer and fewer FDD devices remaining inoperation, the operator may decide to use both the UL and DL bands forTDD operation. This is illustrated in FIG. 12 where FDD LTE 1210 onlyhas one subframe in use for UL and one for DL and the remainder areidle. There are two TDD LTE networks 1220 and 1230 each respectivelyusing the FDD LTE 1210 UL and DL channels, resulting the three networkssharing the two channels as show in FDD+TDD LTE 1240. The sameflexibilities and constraints apply as described previously, and therecan be a single controller of all 3 networks or multiple controllers.The two TDD networks can be operated independently, or by using CarrierAggregation techniques.

An operator may also choose to forgo TDD altogether but instead add asecond FDD network in the same spectrum as an existing FDD network, butwith the Uplink and Downlink channels swapped. This is illustrated inFIG. 13 where FDD LTE 1310 network is very asymmetrically utilized infavor of the DL channel, so only one subframe is used for UL, and asecond FDD LTE 1320 network is also very asymmetrically utilized infavor of the DL channel, but notice that in FIG. 13 the channelallocation for FDD LTE 1320 is swapped, with the FDD Downlink channelshown above the FDD Uplink channel, contrary to the channel order forFDD LTE 1310 or as shown in prior figures. In the case of both FDD LTE1310 and 1320, the DL channel leaves one DL subframe idle thatcorresponds with the one UL frame that is used by the other network.When the networks are combined as shown in FDD+TDD LTE 1230, all of thesubframes in both channels are DL, except for subframes 1231 and 1232.Thus, 90% of the subframes are devoted to DL, which better matchesmobile traffic patterns as they have evolved than symmetric spectrumallocation for UL and DL.

Also, this structure enables the controller (or controllers) that managethe network to dynamically change the number of UL and DL subframesallocated to each network on a subframe-by-subframe basis, affordingextremely dynamic UL/DL traffic adaptation, despite the fact that FDDdevices are using both networks.

As with the combined FDD/TDD networks previously described, the sameconstraints apply for FDD mode in that the LTE devices must receivesufficient control and timing information to remain connected andoperate well, and they need sufficiently regular and adequate number ofUL frames.

The two FDD networks can be operated independently or through CarrierAggregation.

In another embodiment, the control information transmitted by the DLchannel an existing active network (e.g. in FIGS. 9, 11, 12 and 13 FDDLTE 910, FDD LTE 1110, FDD LTE 1210, or FDD LTE 1310) is used by a newnetwork (or networks) using the same channel (e.g. in FIGS. 9, 11, 12and 13 TDD LTE 920, TDD LTE 1120, TDD LTE 1220 and TDD LTE 1230, or FDDLTE 1320) to determine which subframes and/or resource blocks and and/orother intervals will be idle. In this way, the new network(s) candetermine when it is able to transmit (whether DL or UL) withoutinterfering with the existing active network. This embodiment may makeit possible to concurrently use the spectrum of the existing activenetwork without any modification of the existing active network orrelying upon any special connection to the existing active network'scontroller, since it is just a matter of the controller of the newnetwork(s) receiving what is already in the DL transmission from theexisting active network. In another embodiment, the only modification tothe existing active network is to make sure it enables the newnetwork(s) to transmit essential control and timing information tomaintain connections with UEs. For example, the existing active networkcould be configured to not transmit during times when essential timingand synchronization information are being transmitted, but otherwiseoperate unmodified.

Although the above embodiments of concurrently supporting networks inthe same spectrum used the LTE standard for examples, similar techniquescan be utilized with other wireless protocols as well.

4. Utilizing DIDO MU-MAS Concurrently with Actively Used Spectrum

As disclosed in Sections 1 and 2 and in the Related Patents andApplications, the DIDO MU-MAS techniques dramatically increase thecapacity of wireless networks, improve reliability and throughput perdevice, and make it possible to reduce the cost of devices as well.

In general, DIDO technology operates more efficiently in TDD than FDDnetworks because the UL and DL are in the same channel and, as a result,training transmission received in the UL channel can be used to derivechannel state information for the DL channel by exploiting channelreciprocity. Also, as described, TDD mode inherently better suits theasymmetry of mobile data, allowing for more efficient spectrumutilization.

Given that most of the world's current LTE deployments are FDD, byutilizing the techniques disclosed in Section 3, it is possible todeploy a TDD network in spectrum actively used for FDD, and DIDO can beused with that new TDD network, thereby dramatically increasing thecapacity of the spectrum. This is particularly significant in that, UHFfrequencies propagate far better than microwave frequencies, but mostUHF mobile frequencies are already in use by FDD networks. By combiningDIDO-based TDD networks with existing FDD networks in UHF spectrum, anexceptionally efficient TDD network can be deployed. For example, Band44 is a TDD band from 703-803 MHz, overlaying a large number of 700 MHzFDD bands in the U.S. Band 44 devices could be used concurrently in thesame spectrum as 700 MHz FDD devices, enabling DIDO TDD in primespectrum.

DIDO does not add significant new constraints to the spectrum combiningtechniques described above. The DRAN 104 shown in FIG. 1 would eitherreplace the existing eNodeBs in the coverage area, or coordinate withthe existing eNodeBs 401, as shown in FIG. 4 per the subframe (orresource block) sharing techniques described above.

Notably, if the DIDO system is controlling the entire system andproviding the eNodeB for the FDD network, then DIDO can use a trainingsignal such as the SRS UL from the FDD devices so as to decode viaspatial processing the UL from multiple existing FDD devices at the sametime and within the same frequency band, thus dramatically increasingthe spectral efficiency of the existing FDD UL channel and also reducingthe UL power required (and/or receiving better signal quality) since thedistributed DIDO APs are likely closer to the UEs than a single cellularbase station, and also can utilize signal combining techniques, such asmaximum ratio combining (MRC) or other techniques as describedpreviously for DIDO.

Thus, DIDO can replace existing eNodeBs and simultaneously use existingspectrum with DIDO TDD devices, while also applying the benefits of DIDOto the UL of the existing FDD devices that are already deployed.

We claim:
 1. A system of two overlapping wireless networks utilizing thesame spectrum comprising: a plurality of wireless user devices (“UEs”) afirst wireless network comprising a first plurality of wireless basestations (“BTSs”) within a coverage area larger than the range of anyone BTS, wherein the UEs remain continuously coupled to the firstwireless network as the UEs move throughout the coverage area throughuse of cellular handovers between BTSs; a second wireless networkcomprising a second plurality of BTSs within a coverage area larger thanthe range of any one BTS, wherein the UEs remain continuously coupled tothe second wireless network as the UEs move throughout the coverage areawith no handovers between BTSs; and the first wireless network operatingin FDD mode and the second wireless network operating in TDD mode,wherein both wireless networks can be received by the plurality of UEs,wherein a spectrum of the first wireless network overlaps, at least inpart, with a spectrum of the second wireless network.
 2. The system inclaim 1 further comprising the second wireless network operating in TDDmode operates in same spectrum as the FDD downlink of the first wirelessnetwork.
 3. A method implemented within a system of two overlappingwireless networks utilizing the same spectrum comprising: a plurality ofwireless UEs; a first wireless network comprising a first plurality ofwireless base stations (“BTSs”) within a coverage area larger than therange of any one BTS, wherein the UEs remain continuously coupled to thefirst wireless network as the UEs move throughout the coverage areathrough use of cellular handovers between BTSs; a second wirelessnetwork comprising a second plurality of BTSs within a coverage arealarger than the range of any one BTS, wherein the UEs remaincontinuously coupled to the second wireless network as the UEs movethroughout the coverage area with no handovers between BTSs; and thefirst wireless network operates in FDD mode and a second wirelessnetwork operates in TDD mode, wherein both wireless networks can bereceived by the plurality of UEs, wherein a spectrum of the firstwireless network overlaps, at least in part, with a spectrum of thesecond wireless network.
 4. The method in claim 3 further comprising thesecond wireless network operating in TDD mode operates in same spectrumas the FDD downlink of the first wireless network.